Hydronephrosis

What is hydronephrosis?

Hydronephrosis is the dilation or stretching of the kidneys that occurs when there is an obstruction or partial blockage to the flow of urine at some point along the urinary tract. Normally, urine flows from the kidneys through the ureters and into the bladder. If there is a blockage that prevents the urine from draining properly, urine can back up in the kidneys and hydronephrosis occurs.

What causes hydronephrosis?

Some children are born with hydronephrosis, while others can develop it as a result of a kidney stone or injury to the urinary tract. There are many different kinds of urinary tract obstructions that can lead to hydronephrosis. The most common type is at the junction where the ureter joins the kidney, called the ureteropelvic junction. This blockage is caused by an abnormal narrowing of the ureter at this location. The next most common site of narrowing is where the ureter meets the bladder, called the ureterovesical junction.

Some conditions commonly associated with blockage of the kidneys include:

Who gets hydronephrosis?

Helpful resources:

What are the signs and symptoms of hydronephrosis?

Children with mild hydronephrosis may have no symptoms at all, or the condition may improve or disappear within the first year of life. In more severe cases when the kidneys are affected, symptoms may include pain with urination, hematuria (blood in the urine), high blood pressure and infection. Symptoms may not occur until months or years after the hydronephrosis has been detected.

What tests are used to detect hydronephrosis?

Hydronephrosis can be detected pre-birth through a routine prenatal ultrasound. Hydronephrosis is not a diagnosis; it is a finding that indicates an obstruction. Once the cause of the obstruction is decided, the appropriate treatment will be determined.

If hydronephrosis is discovered after birth, or if a child develops hydronephrosis, the underlying cause of the obstruction will need to be determined by utilizing one or more of the following tests, depending on the severity of the condition:

Voiding cystourethrogram (VCUG)

Renal ultrasound (RUS)

Renal Scan (MAG 3 with lasix)

Magnetic resonance imaging (this is rarely needed)

If your child experiences any of the symptoms of hydronephrosis, seek medical attention. If your child has already been diagnosed, it is important to continue regular follow-up appointments to evaluate if the condition is worsening or improving.

How is hydronephrosis treated?

At some point, your child’s hydronephrosis will be classified (as mild, moderate or severe) and graded (from 1 to 4, with 4 being the most serious) as unilateral (occurring in one kidney) or bilateral (occurring in both kidneys). Based on these classifications, a treatment plan will be determined.

Treatment of hydronephrosis varies depending on the cause and the severity of the condition. In cases caused by mild obstruction, the child may only need to be monitored with regular ultrasound scans, because the condition may improve or resolve on its own. In moderate-to-severe cases of hydronephrosis, severe unilateral hydronephrosis or severe bilateral hydronephrosis, treatment may include antibiotics with serial radiologic testing (scans).

Imaging studies are used to decide if surgical treatment is necessary. Surgery is usually necessary to correct the cause in severe unilateral and bilateral cases, but may be beneficial in some moderate cases as well.

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